1. Field of the Invention
The present invention relates generally to a detection circuit and more particularly, to a circuit for detecting an Open/Shorted LED conditions in an electrical circuit.
2. Description of the Related Art
Electrical circuits generally have one or more load components connected in series or parallel with a current source and with various other components in the circuit. Fault in one or more load components may result in change in the voltage drop across other component of the circuit. Such faults may results in damage of one or more active or passive components of the circuit. One such fault condition is Open/Shorted load conditions.
In an electrical circuit, the open load condition is a condition where the output current is less than a predetermined minimum current. Further, the shorted load condition is a condition where the output current is more than a predetermined minimum current. The shorted load condition results in increased load current, which may cause damage to active or passive components of the circuit. A number of methods and circuits are known to determine an open load or shorted load conditions.
However, such method and circuits has to be implemented using at least two different circuits for measuring Shorted and Open load conditions separately. Therefore, results in a complex and bulky circuit. Such circuits generally occupy large space and are not preferred considering the modern day technology of integrated circuits.
Further, considering the transfer characteristics of the loads such as resistive loads, the detection of open/shorted conditions of such loads is generally not feasible, hence the accurate detection is not obtained. However, for loads such as LEDs, controlling average current through the LEDs and the detection of open/shorted LED condition in a circuit is feasible since the intensity of lightening is proportional to the average current flowing through the LEDs. Further, the characteristic of diodes is that above the cut-in voltage, the incremental resistance is very small, and hence makes the detection of open/shorted LED condition feasible. One such implementation is illustrated according to the FIG. 1 of the present invention.
As illustrated in FIG. 1, a conventional electrical circuit is disclosed, wherein the circuit comprises a battery, an inductor and one or more LED and a sensing resistor. The inductor is connected in parallel to the LED's and the battery (power source) provides the DC voltage Vbat. The negative terminal of the battery is connected to the ground and the positive terminal is connected to the inductor and the cathode terminal of LED's. The sensing resistor is in series with the parallel circuit elements and a sensing voltage can be obtained across the sensing resistor. The current control action in this conventional circuit further employs a variable switching signal ‘Φ’ that operates a switch to connect the parallel circuit elements to the sensing resistance. However, the circuit fails to identify the faulty condition such as an open LED or shorted LED.
Hence, there is a well-felt need for an embedded circuit, which is capable of detecting an open/Shorted LED conditions at the output of any electronic circuit.